APU EGT Indicating System Component Location
Figure 1 (Sheet 1)
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A 737-300/400/500MAINTENANCE MANUAL
//////////////////////// / GTCP85-129 SERIES / / ENGINES / ////////////////////////
SEE D
SEE C
C
THERMOCOUPLE
PROBE
HARNESS BALANCING RESISTOR
1
D
1 AIRPLANES WITH THE HARNESS BALANCING RESISTOR
APU EGT Indicating System Component Location Figure 1 (Sheet 2)
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////////////////////////A / GTCP85-129 SERIES /737-300/400/500/ ENGINES /MAINTENANCE MANUAL ////////////////////////
SEEF
SEE E
E
THERMOCOUPLE
PROBE
ENGINE
THERMOCOUPLE
HARNESS
2
F
2 AIRPLANES WITHOUT THE HARNESS BALANCING RESISTOR
APU EGT Indicating System Component Location Figure 1 (Sheet 3)
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5. EGT Indicator
_____________
A. The EGT indicator is a millivoltmeter in a hermetically sealed case. The EGT indicator has an electrical plug on the rear side. The electrical plug connects the EGT indicator to the circuit for the EGT indicating system. The dial of the EGT indicator shows temperatures from 0 to 850°C. There are color bands to show the usual and dangerous temperature ranges.
6. Operation (Fig. 2)
_________
A. The EGT indicating system has a thermocouple probe connected to the EGT indicator on the P5 forward overhead panel. The airplane electrical system only supplies the lighting for the EGT indicator.
B. The temperature difference between the thermocouple probe (hot junction) and the EGT indicator (cold junction) makes the electrical signals in the circuit for the EGT indicating system. The difference between these electrical signals is in proportion to the difference in temperature between the thermocouple probe and the EGT indicator. Because the electrical signal only corresponds to a temperature difference, the ambient temperature of the control cabin must be added to the temperature difference to get the actual temperature of the exhaust gases. The temperature of the control cabin has small variations. The EGT indicator has a bimetal (thermostatic) spring to make allowances for these temperature changes. The EGT indicator does show the correct temperature for the exhaust gases in all ambient conditions.
EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. AIRPLANES WITHOUT THE ETC ú
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////////////////////////A / GTCP85-129 SERIES /737-300/400/500/ ENGINES /MAINTENANCE MANUAL ////////////////////////
EGT RESISTOR
THERMOCOUPLE
UPPER
PROBE
SHROUD
JUNCTION
